In order to increase system transmission bandwidth, a carrier aggregation technology is introduced into a Long Term Evolution Advanced (LTE-A) system.
During carrier aggregation, user equipment (UE) usually can aggregate a larger quantity of downlink carriers, while a much smaller quantity of uplink carriers. Generally, based on channel non-reciprocity, for measurement of some downlink channels, measurement of the downlink channel is obtained using a channel non-reciprocity feature, for example, a precoding matrix index (PMI) and an uplink sounding reference signal (SRS). Because UE's downlink carrier aggregation capacity is greater than its uplink carrier aggregation capacity, no uplink transmission is present on some time division duplex (TDD) carriers for downlink transmission of the UE. To ensure timely SRS transmission, carrier switching is required. For example, in a first subframe, a carrier 1 and a carrier 2 are used for downlink transmission. When SRS transmission is required in a second subframe, carrier switching is performed. The carrier 2 is changed to a carrier 3 and the carrier 3 is used to transmit the SRS. In addition, transmit power for the SRS needs to be controlled to ensure that the SRS is received correctly.
Parameter settings of other approaches SRS power control solution depends on some parameters related to physical uplink shared channel (PUSCH) power control, while the UE cannot obtain the parameters related to PUSCH power control on the switched-to carrier used for SRS transmission. As a result, SRS power control is not possible, and the SRS cannot be received correctly.